Hello,
Can someone verify my diagram of connecting the Arduino Fio with an ID-12 RFID Reader? I figured that using a Logic Level Converter is the proper way to do it, but Im not sure if I should have a DC-DC step up board between the two to provide power to the ID-12 or if the LLC can step up the voltage as well.
http://farm9.staticflickr.com/8461/7903 … 72f990.jpg
Or is this correct?
I can say the first wiring diagram won’t work. The LLC and the ID-12 board need a supply of ~5V to do their functions. The top diagram doesn’t provide that. The 2’nd/bottom diagram would seem to, though I wonder if there isn’t an easier alternative. The FIO board has a 3.3 V regulator (U2) and another device, U1, which is a battery charger IC. Depending on how you apply voltage to the FIO, that IC may/may-not be active and making Vbatt. Vbatt is available on JP-2. Now I think Vbatt may be as high as 4.5 V (depends on how the FIO board is configured and I’ve not looked into this) and the ID-12 spec says it’ll run on 4.6 V. So it may be possible to run the ID-12 board off Vbatt w/o an additional DC/DC converter. It’s by no means guaranteed but if this is just for your usage you might want to look into it.
Otherwise you’ll need some other supply of ~5V. It might be easier to make a board that takes the USB 5V and funnels that to the LLC and ID-12 boards … assuming you’re using USB to power the circuits. And I think that just maybe the USB Vin is sent to a header/pin that you can solder a wire to … and thus send it to the LLC and ID-12 w/o the need for any additional board. What flavor of FIO are you using ? V1 or V3 or ???
Mee_n_Mac:
I can say the first wiring diagram won’t work. The LLC and the ID-12 board need a supply of ~5V to do their functions. The top diagram doesn’t provide that. The 2’nd/bottom diagram would seem to, though I wonder if there isn’t an easier alternative. The FIO board has a 3.3 V regulator (U2) and another device, U1, which is a battery charger IC. Depending on how you apply voltage to the FIO, that IC may/may-not be active and making Vbatt. Vbatt is available on JP-2. Now I think Vbatt may be as high as 4.5 V (depends on how the FIO board is configured and I’ve not looked into this) and the ID-12 spec says it’ll run on 4.6 V. So it may be possible to run the ID-12 board off Vbatt w/o an additional DC/DC converter. It’s by no means guaranteed but if this is just for your usage you might want to look into it.Otherwise you’ll need some other supply of ~5V. It might be easier to make a board that takes the USB 5V and funnels that to the LLC and ID-12 boards … assuming you’re using USB to power the circuits. And I think that just maybe the USB Vin is sent to a header/pin that you can solder a wire to … and thus send it to the LLC and ID-12 w/o the need for any additional board. What flavor of FIO are you using ? V1 or V3 or ???
Im using the [Fio v1.0. The Fio is hooked to a 3.7V Li-Ion battery, and for the moment it wont have access to a remote power supply unless the device stops working, in which case the battery needs a recharge. Im not bothering with the fancy voltage monitoring or extra power cables for now. So powering via USB is out of the question.
I measured VBATT at about 3.86V, which is close to my 3.7V Li-Ion Battery. Thats still 0.64V too low to power the ID-12. The only other alternative I can think of is using a MAX756 or LT1302 to boost the voltage, but thats the same as using a DC-DC converter.](https://www.sparkfun.com/products/10116)
Well then in your usage it seems there’s no way around using a DC/DC converter. The only other possibility is using another battery in series with the Li-Ion you have to get ~5V. But then you’d have the problem of charging this “extra” battery.
Mee_n_Mac:
The only other possibility is using another battery in series with the Li-Ion you have to get ~5V. But then you’d have the problem of charging this “extra” battery.
Well that and I run into all sorts of problems with the Li-Ion battery becoming a fire-hazard. According to the Sparkfun website, thats not recommended.
Glad though that I got one of my two ideas verified. I figured I would need either an external 5V or a DC-DC converter. Since external is out, DC-DC it is.
Thanks for the help.
UNTEngineer:
Well that and I run into all sorts of problems with the Li-Ion battery becoming a fire-hazard. According to the Sparkfun website, thats not recommended.
Hmmm, not sure why running Li-Ion/Li-Po’s in series to get a higher voltage should present a fire hazard, at least at the current levels I’d expect in your usage. Nonetheless such an arrangement would be a PITA to charge.
Carmack says … I see a DC/DC in your future. :mrgreen:
Mee_n_Mac:
Hmmm, not sure why running Li-Ion/Li-Po’s in series to get a higher voltage should present a fire hazard, at least at the current levels I’d expect in your usage.
I was trying to remember what I had read before on the topic; I mis-remembered. I was incorrect to say the bit about it being a fire-hazard (but it applies to Li-Ion batteries when you’re pulling too much current). From the [850mAh page:
Like any other battery type, you need to be careful when using batteries in parallel or series. Two in series will give you ~7.4V, while in parallel will increase the “drain-time”. A couple quick pointers:
Always use batteries of the same type and voltage level
Never mix batteries at different stages of charge level (i.e. one full, one half-full)
Always use an appropriate charger for the battery type and size
Never charge batteries in parallel unless you have a charge balancer
Make sure that you are informed when you are using something potentially dangerous like Lithium-based batteries.
I know that there is built-in protection against over voltage, over current, and minimum voltage, so I would think putting them in series/parallel for increased current or voltage would have issues. Im thinking I wanna try this though, while its a no-no, Ive got a few spare batteries to try it.](https://www.sparkfun.com/products/341)
